The BOLD signal is often used as a direct index of neuronal
activity to study changes with aging. However, profound changes in
cerebrovascular properties in older adults may lead to biases in the
interpretation of BOLD signal differences between young and old. Here we show
that changes in baseline blood flow, reactivity to hypercapnia and
calibration parameter M are present even in healthy aging. These changes may
lead to underestimation of metabolic changes with aging.